In the crowded field of coffee makers, there are taught thousands of devices and methods for making coffee. Many of these make a variable quantity of coffee and/or variable strength coffee. This is accomplished by a myriad of devices from percolators, 1.5 to simple drippers, through complex commercial systems. The resulting quality of the coffee is hotly debated in every coffee shop and now in every coffee blog. Every new device and method claims to be an improvement commonly without any objective justification.
In commercial vending systems, it is well understood that it is necessary to achieve the correct strength in the reconstituted mixture of coffee, soda, or juice. To this end various methods are used to ensure proper strength. Usually this involves metering the concentrate and water in a prescribed ratio. In U.S. Pat. No. 6,387,424 electric conductance of the mixture is measured to estimate the percentage of “Total Dissolved Solids” (% TDS) of the mixture. The % TDS is simply the ratio of the mass of the solid material to the total mass of the resulting mixture.
Only a few coffee patents even mention the concept of % TDS as a quantitative measure of the strength of the coffee. In U.S. Pat. No. 7,047,870 Gantt presents an apparatus and method for varying the strength of coffee in “pod” systems. In these systems, a pre-measured volume of ground coffee is packaged in a filter pod. The pod is placed in a machine and hot water is forced through it to produce a coffee beverage. In the method described, the apparatus removes varying percentages of the solid coffee to produce a “light,” “regular,” or “strong,” cup of coffee. This is a disastrous recipe since it also changes the “Percent Extraction” (% EXT). This is the fraction of the original coffee grounds that is dissolved out into the resultant solution. A 20% TDS+/−1% is generally considered the ideal extraction percentage. Above 22% EXT removes too much of the solids including compounds that make the resulting coffee taste bitter. Below 18% TDS presents an “under developed” taste.
It is typical of drip coffee makers to under extract the coffee. So a user that desires a stronger coffee has no choice but to use more grounds. Collectively, this results in a tremendous waste of coffee in the $18 billion domestic market.
The Specialty Coffee Association of America (SCCA), among others, promotes brewing charts to assist in making an ideal cup of coffee. These are used with an optical refraction meter or electrical conductivity meter to estimate % TDS. With the help of the chart the % EXT may also be inferred. The published advice however is limited to statements to the effect of “keep the water in contact with the grounds longer to get more extraction.” This advice has no precision and leaves the aspiring brewer with a frustrating task.
To further the art of coffee making, applicant disclosed a novel brewing device in its U.S. application Ser. No. 12/486,514 filed on Jun. 17, 2009, a copy of which is incorporated by reference herein. This apparatus was taught to be capable of making an ideal cup of coffee in accordance with the “Gold Cup” standard as defined by the Specialty Coffee Association of America, the Norwegian Coffee Counsel and other trade organizations and the governing bodies of such standards and, in doing so, to produce coffee according to any taste preference.
Most commercially available coffee makers provide inconsistent and unpredictable results. Some of them produce coffee which is weak and underdeveloped while others produce coffee which is strong and bitter. Such devices, to be successful, require the ability to repeatedly introduce the appropriate amount of water, at the appropriate temperature with the appropriate amount of ground coffee, at a suitable grind controlling the interaction between the grinds and water appropriately.
Most coffee makers work under the drip system where water dribbles into the brewing basket and leaches through the coffee bed as more water is introduced. This continues before the grinds are uniformly wetted. For a manual 1-cup drip cone, the state of the art is to use trial and error to find a set of steps that produce a desired product. The resulting recipe is recorded and then repeated. The task is even more daunting for the designer of a home drip machine which needs to produce a variety of volumes.
A more controlled method is needed with sufficient variables so that the ideal brew point can be achieved each time. Moreover, the brew variables including, but not limited to, darkness of roast, ground size and volume of the brew all need to be accounted for to produce a desired product each time.
As noted in applicant's U.S. application Ser. No. 13/177,410, filed on Jul. 6, 2011, the disclosure of which is incorporated by reference, teaches a method of developing an ideal coffee beverage based upon user inputs including taste, body and strength profile as represented by total and dissolved solids (TDS) and percent extraction (% EXT). Based upon these values, the appropriate amount of coffee is delivered to a brewing chamber and the amount of water and contact time between the ground coffee and water is determined including an accounting for agitation. In doing so, the following equations were taught to achieve the appropriate taste/body and strength profiles as selected by the user.Water=Dose*% EXT/% TDS  (1)BrewTime=A+B*% TDS+C*Grind+D*Roast+E*WM+F*Temerature  (2)
The constants A, B, C, D, E, and F depend on the particular brew process employed. In another preferred embodiment, the amount of Water may be introduced to the system and the Dose is computed byDose=Water*% TDS/% EXT  (3)
The steps required are precise and complex suggesting a complex and expensive brewing apparatus. Therefore it is an object of the present invention to disclose simple methods of achieving these tasks in an inexpensive device.
This and further objects will be more readily apparent when considering the following disclosure and appended claims.